Ability to partially specialize implementation_level

[sohail_]

Please add the ability to partially specialize implementation_level using enable_if. The use I would appreciate is:

template<typename T, typename Enable=void>
struct implementation_level;

template<typename T>
strut implementation_level<T,enable_if<my_condition<T> >::type >
{
   make_never_serialized_somehow;
};

If the above is not possible, please add an example to the documentation expressing how to achieve the above for a class of possibly unrelated types.

Thanks